Control for air conditioning systems



july1l,147.. 'c. D. GRAHAM S 2,423,382

CONTROL FOR AIR CONDITIONING SYSTEMS Filed Nov. 20, 1943 2 Shets-Sheetl Lg a M I I I 000$ //////l Vd 24 l; u v 12. Q

July 1, 1947. c. D. GRAHAM CONTROL FOR AIR CONDITIONING SYSTEMS 2 Sheets-Sheet 2 Filed Nov. 20, 1943 v INVENTOR.

July 1, 147

Unit

CONTROL F03 AIR CONDITIONING SYSTEMS Charles D. Graham, Dayton,

General Motors Corporation,

Ohio, assignor to Dayton, Ohio, a

corporation of Delaware Application November 20,

Claims.

This invention relates to refrigerating apparatus and more particularly to an improved arrangement for controlling the flow of refrigerant in a fixed restrictor type of refrigeration system.

One object of this invention humidity control in an air conditioning system a fixed restrictor type of refrigerant fiow he: other object of this invention is to utilize he refrigerant gas for vaporizing a portion liquid refrigerant flowing through the fixed or. it another object of this invention is to proportion of the refrigerant from the high side of the compressor to the low side of the compressor in a fixed restrictor system.

A further objectof this invention is to provide an improved air conditioning system in which the flow of refrigerant to the evaporator is throttle-d at light sensible cooling loads and in which the ratio of latent cooling to sensible cooling is increased upon a decrease in the demand for sensible cooling.

Further objects and advantages of the present invention will be apparent from the following scription, reference being had to the accomylng drawings, wherein a preferred form of one present invention is clearly shown.

in the drawings:

l diagrammatically'shows an air conditioning system incorporating my improved controi; and

Fig. 2 is a diagrammatic view showing a modification oi the air conditioning system shown in Fig. 1.

Referring now to the drawings, the air to be conditioned is passed through an air conditioning chamber It by means of a fan H, which may be driven in any suitable manner as by the electric motor it. This air is then passed to the space to be conditioned it, through the air outlet M. A fresh air inlet l8 and a return air inlet are provided in accordance with standard practice. Dampers 22 and 24 may be used for controlling the proportions of fresh and return air admitted to the chamber Hi. These dampers may be manually operated or automatically operated in any suitable manner. Thus temperature or humidity responsive means, or a combination of both, may be used for controlling either one or both of these dampers, in accordance with either the condition of the inside air, the outside air or a combination of both.

An evaporator Kati ride means for icy-passing a 26 is provided in the chamber is to improve the 1943, Serial No. 511,079

Ill directly in the path of the air to be conditioned.

Reference numeral 28 designates a conventional motor-compressor unit which is used in compressing the refrigerant and discharging a compressed refrigerant into the line .30 which leads to the condenser 32. The refrigerant condensed in the condenser 32 collects in the receiver 34 and is conveyed to the evaporator through the refrigerant line 36, in which there is mounted a fixed restrictor 38. The fixed restrictor 38 is preferably of the well known type which includes a relatively long, narrow capillary passage which serves to reduce the pressure of the refrigerant as it flows through the restricted passage into the evaporator 26, which is maintained under suction by operation of the motor-compressor unit 28. Reference numeral 80 designates the suction line leading from the evaporator to the motor-compressor unit 28. I

It has been found that frequent cycling of the motor-compressor unit is objectionable in an air conditioning system since the change in the temperature and the humidity of the air discharged from the chamber l0 upon cycling is very noticeable in the conditioned space.

I have found that the flow of refrigerant through a fixed restrictor may be varied by the application of heat to the liquid refrigerant flowing from the receiver to the fixed restrictor. By adding heat to the liquid refrigerant so as to partially vaporize the refrigerant'passing through the fixed restrictor the amount of refrigerant which passes through the fixed restrictor is reduced.

In order to heat the liquid refrigerant flowing from the receiver 34 to the restrlctor 38, I have provided a hot refrigerant gas by-pass line 42 in which there is provided a heat interchanger M and a second fixed restrictor 46. A valve 48 controls the flow of refrigerant through the by-pass 42. The valve 48 is controlled by means of a thermostat 50 located in the path of the air leaving the evaporator 26. The heat interchanger 44 is of standard construction and includes one pass through which the hot compressed gas flowing through line 42 passes, and a second pass through which the liquid refrigerant in the line 36 flows. The heat interchanger could surround the restrictor 38, if desired.

By virtue of the above described arrangement the flow of refrigerant to the evaporator may be controlled without reducing the suction pressure an excessive amount, since the hot gas flowing through the by-pass 42 in which the heat interchanger 44 is located is added to the gas return= '3 ing from the evaporator to the motor-compressor unit 28. A restrictor 46 is provided in the by-pass line 52 and serves to reduce the pressure of the gas flowing through the by-pass 42 so as to relieve the valve 48 from taking the entire pressure drop. This restrictor may be omitted if desired.

The valve 48 is preferably a modulating valve, although an on and oil. valvecould be used but would not ive the gradual control which a modulating valve would obviously give.

For purposes of illustration I have shown a room thermostat 52 for controlling the motorcompressor switch 54. The thermostat 52 operates the switch 54 through the bellows 56 in accordance with well known practice. Electrical energy is supplied to the motor-compressor unit 25 through the power lines designated by the reference numeral 58.

In Me. 2 of the drawing I have shown a somewhat similar arrangement, including an air conditioning chamber I lnethrough which the air to be conditioned is circulated by means of a fan iii driven by a motor I I2. The conditioned air is discharged through the outlet I I4 into the conditioned space 6. A fresh 'air inlet H and a return air inlet I20 are provided for supplying air tothe conditioning chamber I I0 in accordance with well known practice. Dampers I22 and I24 are provided for controlling the proportions offresh air and return air entering the conditioning chamber III). These dampers may be controlled by means of any suitable temperature or humidity controls (as explained in connection with dampers'IB and 20 of Fig. 1); tioned is cooled by means of the evaporator sections I 25 and I20 which are arranged in parallel refrigerant flow relationship. A pair of restrictors M8 and. E39 are provided as shown for controlling the flow of refrigerant to the evaporator sections 825 and I25 respectively. The restrictors I 30 and I39 are preferably of the type including a relatively long, narrow capillary passage through whichthe liquid is required'to pass on its way to the evaporator. A motor-compressor unit I28 is provided for withdrawing the refrigerant vapor from the evaporator sections I25 and I 28 in ac- The air to be condicordance with standard practice. A valve I29 is placed in the suction line and'is of the type which prevents the pressure within the evaporator sections S25 and I26 from becoming low enough to freeze the condensate on the evaporator sections 25 and 520. The valve I 29 include the usual pressure line l3I. The compressed refrigerant is discharged into the condenser I32 wherein it is condensed before entering the receiver I34. A valve M8 is provided in the line I42 leading to the evaporator section I 25. A valve I48 is controlled by means of a thermostat I50 located in the path of the air leaving the evaporator sections I25 and idii. It will be noted that the thermostat I50 is placed at the outlet of the fan, whereby the air flowing thereover is a thorough mixture of the r 1 5 over the two evaporator section I25 nrposes of illustration I have shown a :at I52 for controlling the mercury con- ..-et switch I54, arranged in the power line I58, which supplies electrical energy to the motorcompressor unit I28. The usual form of bellows ass is connected to the thermostatic bulb I52 as shown, for operating the switch I54.

The thermostat I52 is preferably adjusted so as to turn oil the motor-compressor unit I28 whenever the temperature within the conditioned space falls below a predetermined value. Under normal conditions the thermostat I52 will seldom turn off the motor-compressor unit as the amount of cooling will largely be controlled by the thermostat I50 which operates the valve I48. As the temperature of the air supplied to the conditioned space H6 falls below a predetermined value, indicating that the air'conditioning system has more capacity than required for reducing the dry bulb temperature in the conditioned space, the valve I48 will begin to close and throttle the flow of refrigerant to the evaporator section I25. As the flow of refrigerant to the evaporator section I25 is decreased, the total amount of cooling will be reduced. Closing of the valve I48, either partially or completely, will tend to reduce the suction pressure in the evaporator means. The reduction in the suction pressure will tend to reduce the temperature prevailing in the evaporator, but inasmuch as the total amount of effective evaporator surface willbe reduced because of the reduction in the amount of refrigerant supplied to the evaporators, the total reduction in the dry bulb temperature will be less, but the effec tive evaporator surface will remove an increased amount of moisture as a result of the lower temperature.

While I prefer placing the thermostats 50 and I50 in the outgoing air stream, they could be located directly in the conditioned space or in the path of the air entering the evaporator. The location of the thermostat depends partly upon the type of air conditioning installation and the effect desired. Wet bulb thermostats or humidistats couldbe substituted for the dry bulb thermostats for some purposes.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow:

What is claimed is as follows:

1. In a. refrigerating system, evaporator means, means for flowing air in thermal exchange relationship with said evaporator means, condenser means, refrigerant compressor means for-withdrawing vaporized refrigerant from said evaporator means and for discharging compressed refrigerant into said condenser means, fixed re stricter means controlling the flow of refrigerant from said condenser means to said evaporator means, and means for by-passing refrigerant from a point ahead of said fixed restrictor to a, point beyond said evaporator means in response to a decrease in the temperature of the air leaving said evaporator means.

2. In a refrigerating system, evaporator means, condenser means, refrigerant compressor means for withdrawing vaporized refrigerant from said evaporator means and for discharging compressed refrigerant into said condenserv means, fixed restrict/01 means controlling the flow of refrigerant from said condenser means to said evaporator means, means for by-passing refrigerant from the inlet side of said fixed restricter to the outlet side of said evaporator means, and a valve means controlling the flow of refrigerant through said lay-passing means.

I 3. In a refrigerating system, evaporator means, condenser means; refrigerant compressor means for withdrawing vaporized refrigerant from said evaporator means and for discharging compressed refrigerant-into said condenser means, fixed restrictor means controlling the flow of refrigerant from said condenser means to said evaporator means, means for by-passing req I i a frigerant from the inlet side of said fixed restrictorto the outlet side of said evaporator means, valve means controlling the flow of refrigerant through said by-passing means, and a fixed restrictor in said by-passing means.

4. In a refrigerating system, evaporator means, condenser means, refrigerant compressor means for withdrawing vaporized refrigerant from said evaporator means and for discharging compressed refrigerant into said condenser means, fixed restrictor means controlling the flow of refrigerant from said condenser means to said evaporator means, means for bypassing said evaporator with a portion of the refrigerant, a valve means controlling the flow of refrigerant through said by-passing means, and a fixed restrictor in said by-pass, said by-pass includin a heat interchanger arranged in thermal exchange relationship with the refrigerant flowing to said first named restrictor.

5. In a refrigerating system, evaporator means, condenser means, refrigerant compressor means for withdrawing vaporizedrefrigerant from said evaporator means and for discharging compressed refrigerant into said condenser means, fixed restrictor means controlling the flow of refrigerant from said condenser meansto said evaporator means, by-pass means for flowing compressed refrigerant vapor from the outlet of said compressor means to the-inlet of said compressor means, said by-pass means including means for flowing the compressed refrigerant vapor in thermal exchange relationship with the refrigerant flowing to the evaporator.

6. In a. refrigerating system, evaporatormeans, condenser means, refrigerant'c'ompressor means for withdrawing vaporized refrigerant .from'said evaporator means and for discharging compressed refrigerant into said, condenser means, fixed restrictor means controlling the flow of refrigerant from said. condenser means to said evaporator means, by-pass means for flowing compressed refrigerant vapor from the outlet of said compressor to the. inletof said compressor, said by-pass means including meansfor flowing compressed change relationship with the refrigerant flowing refrigerant vapor in thermal ex-- the conditioned air for controlling the fiow of refrigerant to one of said fixed restrictors, and a pressure regulating valve adjacent the inlet of said compressor for limiting the suction pressure on said evaporators.

9. In a refrigerating system, a first evaporator, a second evaporator, condenser means. compressor means for withdrawing vaporized refrigerant from said evaporatorsiand for discharging compressed refrigerant into, said condenser means, means forfiowing refrigerant from said condensergto said first andisecond evaporators in parallel, a first fixed restrictor controlling the flow of refrigerant to said first evaporator, a second-"fixed restrictor controlling the flow of refrigerant to said second evaporator, valve means responsive to the temperature of the conditioned air for controlling the flow of refrigerant to one of said fixed restrictors, a pressure regulating valve in the suction line leading tothe compressor for limiting the sucti'on'pressure on said evaporators, and means. responsive to the temperature of the conditioned air for starting and stopping the operation of said compressor.

10. In a refrigerating system, a first evaporator, a second evaporator, condenser means,

, compressor means for withdrawing vaporized resure regulating ing to the compressor for limiting the suction a conditioning chamber, means to the evaporator, said by-pass means including a fixed restrictor adjacent the'outlet thereof.

7. In a refrigerating system, a first evaporator, a second evaporator, condenser means, compressor means for withdrawing vaporized refrigerant from said evaporators and for discharging compressed refrigerant into said condenser means, means for flowing refrigerant from said condenser means to said first and second evaporators in parallel, a first fixed restrictor controlling the flow of refrigerant to said first evaporator, a second fixed restrictor controlling the flow of refrigerant to said second evaporator, and valve means responsive-to the temperature of the conditioned air for controlling the fiow to one of said fixed restrictors.

8. In a refrigerating system,- a first evaporator, a second evaporator, condensing means, means including a compressor for withdrawing vaporized refrigerant-from said evaporators and for discharging compressed refrigerant into said flowing refrigerant condenser means, means for from said eondenserto-sa-idfirst-andsecond evaporators in parallel; a first fixed restrictor con-- trolling the fiow of refrigerant to said first. evaporator and for discharging the compressed reorator, a second fixed restrictor controlling the,

fiow of refrigerant to said second evaporator, valve means responsive to the temperature of from said condenser of said fixed restrictors frigerant from said evaporators and for discharging compressed refrigerant into said condenser means, means for flowing refrigerant to said first and second evaporators in parallel, a first fixed restrictor controlling the flow of refrigerant to said first evaporator, a second fixed restrictor controllig the flow of. refrigerant to said second evaporator, means controlling the fiow of refrigerant to' one of said fixed restrictors, and a presvalve in the suction line leadpressure on said evaporators.

11. Airconditioning apparatus for an enclosure comprising in combination, means forming for flowing air through said chamber,- evaporator means arrangedin thermal exchange with the air flowing through said chamber, a condenser, a compressor for withdrawing refrigerant vapor from said evaporator means and for discharging compressed refrigerant into said condenser, a pair offixed restrlctors controlling the fiow of refrigerant tosaid evaporator means, .means for controlling the fiow of refrigerantthrough one and means for preventing the pressure within said evaporator from dropping below .a pre-determined value.

12. Air conditioning apparatus for an enclosure comprising in combination, means forming an air conditioning chamber, blower means for blowing airthrough said chamber into said conditioned space,- an evaporator in said chamber,

condenser: means, compressor means for withdrawing vaporized refrigerant from said evapfrigerant into said condenser means, means for lay-passing said evaporator with a portion of the compressed refrigerant, a fixedrestrictor controlling the fiowof refrigerant through said evaporator, and a...fixed restrictor for controlling the; fiow of refrigerant through said means for by-passin'g the evaporator.

,' 13. Air conditioning apparatus for an enclo- .sure comprising in combination, means forming an air conditioning chamber, blower means for blowing air through said chamber and into said enclosure, an evaporator in said chamber, condenser means, compressor means for withdrawing vaporized refrigerant from said evaporator and for discharging the compressed refrigerant into said condenser, means for by-passing said evaporator with a portion of compressed refrigerant, a fixed restrictor controlling the flow of refrigerant through said evaporator, a fixed restrictor for controlling the flow of refrigerant through said means for by-passing a portion of the refrigerant, and means responsive to the temperature of the conditioned air for controlling the flow of refrigerant through one of said fixed restrictors.

14. Air conditioning apparatus for an enclosure comprising in combination, means forming an air conditioning chamber, blower means for blowing air through said chamber and into said enclosure, an evaporator in said chamber, condenser means, compressor means for withdrawing vaporized refrigerant from said evaporator and for discharging the compressed refrigerant into said condenser; means for Icy-passing said evaporator with a portion of compressed refrigerant, a fixed restrictor controlling the flowof refrigerant through said evaporator, a fixed restrictor for controllin the flow of refrigerant through said means for by-passing the evaporator, means responsive to the temperature of the conditioned air for controlling the fiow of refrigerant through one of said fixed restrictors,

and means responsive to the temperature of the d air within said enclosure for controlling the 0% eration of said compressor.

15. In a refrigerating system, evaporator means, means for flowing air in thermal exchange relationship with said evaporator means, condenser means, refrigerant compressor means for withdrawing vaporized refrigerant from said evaporator means and for discharging compressed refrigerant into said condenser means, means controllin the flow of refri e t fr aid condenser means to said evaporator means,

and means responsive to the temperature of the air leaving said evaporatorv means for Icy-passing refrigerant from a point ahead of said flow con trol means to a point beyond said evaporator means in response to a decrease in the temperature of the air leaving said evaporator means. CHARLES D. GM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name 2,241,033 Huggins M May 6, 19 .11 2,147,678 Smith Feb. 21, 1939 2,165,741 Wolfert July 11, 1939 2,363,273 Waterfill Nov. 21, 19% 2,112,039 McLenegan Mar. 22, 1933 

